In the last ten years the amount of effluent discharged to land has increased substantially. Discharged effluent can leach through the soil affecting groundwater. We need to manage the discharge of effluent to land so that we maintain the quality of our groundwater resources.
On this page: Point and non-point source discharges, When land discharge is suitable , Permitted and consented discharges
Point and non-point source discharges
Threats to our groundwater quality come from either point (specific locations) or non-point sources (wider areas).
Point source discharges and the cumulative effects of non-point source discharges can cause significant levels of contamination in groundwater.
Point sources include:
- septic tanks, leaking effluent treatment ponds and landfills
- leaking underground fuel tanks and pipelines
- mines and waste tailings
- chemical storage areas and timber treatment sites
- waste disposal sites, such as offal holes.
Non-point sources include:
- pesticide and fertiliser applications
- agricultural land use
- application of wastes to land
- saltwater intrusion.
Non-point source discharges
Widespread non-point source discharges such as agrichemicals, animal wastes and nitrogen fertilisers have had a large impact on water quality in shallow aquifers.
Carefully managed land-based effluent treatment systems can be effective in removing nitrogen and other contaminants, maintaining ground and surface water quality.
An increasing number of farm dairies now discharge their waste water to land. However, this only represents about five percent of the total animal waste produced on a dairy farm. The rest comes from stock urinating and defecating directly onto paddocks (non-point source). Find out more about applying effluent to land.
For Waikato Regional Council's rules on discharging farm effluent check out our Regional Plan (Implementation Methods - Farm Effluent Discharges).
The application of fertiliser varies widely with different land uses and across the Waikato region. Application rates are higher for market gardening than for pastoral farming. There is also considerable variation in pesticide use in our region. Pesticides are intensively used in horticulture. Find out more about agrichemicals and spray drift.
Find out more about nitrate, pesticide and microbial contamination.
When land discharge is suitable
Whether land discharge of waste water is suitable depends on the:
- type of soil
- site drainage
- type of waste water
- rate of waste water application.
Where suitable, land discharge is the preferred option for disposal, as it:
- is an environmentally sound method
- promotes the recycling of water and nutrients
- meets many of the concerns of tangata whenua regarding the cultural effects of direct discharge to water.
Permitted and consented discharges
A large number of low impact point source discharges are permitted, such as:
- small on-site waste water discharges
- storm water discharges.
Much larger discharges have the potential to cause a greater impact on groundwater and need to have a resource consent.
The total volume of waste water consented for discharge to land in the Waikato region has increased steadily during the last 15 years to about 460,000 m3 per day.
The volume of discharges to land from manufacturing industries has increased from 81,770 m3 per day in 1997 to about 210,000 m3 per day in 2004.
View our map that shows where the permitted and consented discharges of effluent to land are in our region. Both permitted farm dairy and consented land discharges are concentrated in the:
- Pukekohe and Franklin areas
- Hauraki Plains
- Hamilton Basin
- Reporoa Basin.